BMW E60 5-Series Forum | 5Post.com  
BMW Garage BMW Meets Register Today's Posts  

Go Back   BMW E60 5-Series Forum | 5Post.com > BIMMERPOST Universal Forums > General BMW News and Cars Discussion

Post Reply
 
Thread Tools Search this Thread
      01-15-2023, 12:56 AM   #1
snowbimmer
Colonel
snowbimmer's Avatar
United_States
6327
Rep
2,057
Posts

Drives: 2022 M850 GC - Carbon Black
Join Date: Feb 2017
Location: PDX

iTrader: (0)

Garage List
2022 M850 GC  [9.67]
Hey all, throwing this out there. M550s and M850s run a tire that is around 26.75" OEM diameter. The M5s and M8s run tires that are about 27.75" in diameter.

I've had the M550, two M5s and now have an M850. I feel the tires are just to small for this car - aside from being smaller by an inch in diameter, they also run 8" fronts and 9" rears - as opposed to the M5 & M8 at 9.5" fronts and 10.5" rears.

So, in the spring I am looking at new Vossen wheels and going to 9" fronts and 10.5" rears. I'd like to go up one profile, too, to gain that other inch in height (the wheel wells really need to be filled up a bit more - and it would ride a teensy bit better with more rubber in the side wall).

I took my M5 snow set down to the tire shop to have a look with them on the M850. They mostly fit, however the offsets are just a bit off, but the inch larger tire really looks good. They said a different wheel with the taller tire would be no problem.

I went to my BMW dealership and talked to the tire guy. He waffled about going up a tire size. He checked with the service techs. They said no, don't mess with the OEM diameter. I went to my performance shop guy where I am getting the new wheels. He said don't mess with the OEM diameter. With all the computers, AWD, DSC and what have you, the car could possibly not perform correctly.

If you keep the front and rear wheels within a 1% diameter tolerance between axels and go up a profile size, does the car really care if everything is rolling along, but at a 3% or so, different rate of speed on the axel rpm? I know people have gone wider all the time, but you never really hear about changing diameters that much. I know people do this, just don't know what the consequences are, if any, aside from a speedometer that will be slightly off. (I think it would bring the speedo speed closer to the true speed of the car, thus offsetting the 2-3 mph difference built into BMWs - if I remember which way the math works for this application. I could be wrong - maybe it's the other way around, but I don't feel like checking it now.)

Any thoughts appreciated.

Thx
Appreciate 0
      01-15-2023, 02:31 AM   #2
Atavus
Private First Class
United Kingdom
91
Rep
175
Posts

Drives: BMW M760Li
Join Date: Jul 2021
Location: Slough

iTrader: (0)

BMW or any other German company will expect you to stick to the wheels and tyre sizes they have in their approved list.

If you keep the front and rear circumference as close as the standard tyres are, the car can’t be any the wiser.

Will it give you 100% of the experience BMW designed, who knows?
Appreciate 0
      01-15-2023, 04:01 AM   #3
Llarry
Curently BMWless
Llarry's Avatar
21181
Rep
714
Posts

Drives: 2025 M850ix ordered
Join Date: Jun 2006
Location: Oregon

iTrader: (0)

Garage List
Quote:
Originally Posted by snowbimmer View Post
Any thoughts appreciated.
I see where you are coming from here and count me among the few who thinks you could be on to something. When considering stagger, I always like to work with revs per mile for a particular tire rather than diamrter; revs/mile is a bit more precise. (I use mfr specs or Tire Rack to get revs/mi.)

So, for instance, going up one size in front and rear (and comparing revs per mile to make sure you are not going to mess up your electronic nannies) will almost always work, at least in the electronic sense. Clearance in the wheel well is a separate issue but generally one size up won't cause problems; working with a good tire shop helps here for test-fitting or whatever.

I'm not conversant with the 8er but offhand I see two OE options: 19s with 245/40R-19 & 275/35R-19 and 20s with 245/35R-20 & 275/30R-20. Oh, and now I see you you're proposing a 1.5" width bump both front and rear and an inch wider tire (?) -- that's 25mm -- now you've lost me; I think that is just too extreme.

I would think going to 255 front and 285 rear would not be imprudent, but what you're talking about is pretty radical. My two cents.
__________________
'25 M850ix GC (Ordered)
BMW CCA 30 years
Appreciate 1
snowbimmer6327.00
      01-15-2023, 04:34 AM   #4
335i54n
Captain
350
Rep
604
Posts

Drives: e90 335i, e39 m5
Join Date: Nov 2020
Location: socal

iTrader: (0)

just keep rolling diameter same front and rear close and you be fine. more front tire always helps imo
Appreciate 2
snowbimmer6327.00
Llarry21181.00
      01-15-2023, 05:13 AM   #5
snowbimmer
Colonel
snowbimmer's Avatar
United_States
6327
Rep
2,057
Posts

Drives: 2022 M850 GC - Carbon Black
Join Date: Feb 2017
Location: PDX

iTrader: (0)

Garage List
2022 M850 GC  [9.67]
Quote:
Originally Posted by Llarry View Post
I'm not conversant with the 8er but offhand I see two OE options: 19s with 245/40R-19 & 275/35R-19 and 20s with 245/35R-20 & 275/30R-20. Oh, and now I see you you're proposing a 1.5" width bump both front and rear and an inch wider tire (?) — that's 25mm — now you've lost me; I think that is just too extreme.

I would think going to 255 front and 285 rear would not be imprudent, but what you're talking about is pretty radical. My two cents.
Yes, I'm going 255 front and 285 rear.......only 10mm wider per tire. But the front rim will gain an inch from 8" to 9". The rear rim will go from 9" to 10.5". They are 20" dia wheels.

The M8 runs a 275 on a 9.5" wheel in front and a 285 on a 10.5" wheel in back. The width isn't the problem. My question still remains about the new height vs OEM.
Appreciate 0
      01-15-2023, 05:19 AM   #6
snowbimmer
Colonel
snowbimmer's Avatar
United_States
6327
Rep
2,057
Posts

Drives: 2022 M850 GC - Carbon Black
Join Date: Feb 2017
Location: PDX

iTrader: (0)

Garage List
2022 M850 GC  [9.67]
Quote:
Originally Posted by 335i54n View Post
just keep rolling diameter same front and rear close and you be fine. more front tire always helps imo
That's what I am thinking. By "more front tire" you mean width, correct?
Appreciate 0
      01-15-2023, 05:20 AM   #7
Llarry
Curently BMWless
Llarry's Avatar
21181
Rep
714
Posts

Drives: 2025 M850ix ordered
Join Date: Jun 2006
Location: Oregon

iTrader: (0)

Garage List
Quote:
Originally Posted by snowbimmer View Post
Yes, I'm going 255 front and 285 rear.......only 10mm wider per tire. But the front rim will gain an inch from 8" to 9". The rear rim will go from 9" to 10.5". They are 20" dia wheels.

The M8 runs a 275 on a 9.5" wheel in front and a 285 on a 10.5" wheel in back. The width isn't the problem. My question still remains about the new height vs OEM.
Well, the new "height" (or revs per mile) will change the effective final drive ratio of the car. Your speedometer and odometer will no longer read the same as they did from the factory. Note, however, that German speedometers are deliberately calibrated to read slightly high. Your speedometer may well be slightly more accurate with the larger tires. (Edit: The change will, however, be tiny.)

I don't see a problem with your intended course of action, if -- and only if -- the wider rims don't rub on suspension components, fenders or wheel well. That's where the part about a cooperative and knowledgeable tire seller/shop comes in.
__________________
'25 M850ix GC (Ordered)
BMW CCA 30 years

Last edited by Llarry; 01-15-2023 at 05:50 AM..
Appreciate 2
snowbimmer6327.00
DrFerry6803.50
      01-15-2023, 05:43 AM   #8
snowbimmer
Colonel
snowbimmer's Avatar
United_States
6327
Rep
2,057
Posts

Drives: 2022 M850 GC - Carbon Black
Join Date: Feb 2017
Location: PDX

iTrader: (0)

Garage List
2022 M850 GC  [9.67]
Quote:
Originally Posted by Llarry View Post
I don't see a problem with your intended course of action, if — and only if — the wider rims don't rub on suspension components, fenders or wheel well. That's where the part about a cooperative and knowledgeable tire seller/shop comes in.
I fooled around a lot on "Will it fit?" once I decided on a wheel and knew the offsets. Then took my ideas to my performance shop. He calls his wheel guy, tells him I have an M850 and he tells my guy the wheels and tire size I should use.......they have already test fitted their various wheels to see which works for each make and model. It took him about a minute and a half. We were bang on together, except it took me hours of screwing around. But, he's recommending I stay at OEM height.

The wheels end up about as if I was running a 10mm spacer on my OEMs. Nothing real radical. I just want more meat at each corner and then a little taller if it's doable.

Thx for your comments.
Appreciate 1
Llarry21181.00
      01-15-2023, 08:40 AM   #9
BMWCCA1
BMW Owner Since 1971
2483
Rep
1,510
Posts

Drives: 1964 700 Sport Cabriolet
Join Date: Apr 2014
Location: Central Virginia

iTrader: (2)

Garage List
2013 BMW 128i  [10.00]
Increasing overall tire height (diameter) with the same wheel diameter will only decrease the handling capability of your car with respect to turn-in due to slip-angle. If you're looking for increased comfort, you shouldn't have bought a sport model in the first place! Just get a 530i xDrive and leave those snow tires off your M5!
Appreciate 0
      01-15-2023, 08:55 AM   #10
Llarry
Curently BMWless
Llarry's Avatar
21181
Rep
714
Posts

Drives: 2025 M850ix ordered
Join Date: Jun 2006
Location: Oregon

iTrader: (0)

Garage List
Quote:
Originally Posted by BMWCCA1 View Post
Increasing overall tire height (diameter) with the same wheel diameter will only decrease the handling capability of your car with respect to turn-in due to slip-angle. If you're looking for increased comfort, you shouldn't have bought a sport model in the first place! Just get a 530i xDrive and leave those snow tires off your M5!
I think the OP is more concerned with appearance.
__________________
'25 M850ix GC (Ordered)
BMW CCA 30 years
Appreciate 0
      01-15-2023, 08:59 AM   #11
DanG
Major General
DanG's Avatar
United_States
11406
Rep
7,130
Posts

Drives: 2018 M2 AW DCT
Join Date: Aug 2012
Location: Seattle, WA

iTrader: (1)

Garage List
2018 BMW M2  [7.95]
The M2 crowd has changed the wheel and tire size. As an example I went from 19X9 and 19X10 to 19X9.5 and 10X10.5 BBS wheels. I increased the tire size from 245/35/19 and 265/35/19 to 255/35/19 and 275/35/19.

BBS called my wheels “Tuner Fitment”. I am not running any spacers and I have zero rubbing.
Attached Images
 
__________________
BMWCCA member Puget Sound Chapter
Appreciate 3
Llarry21181.00
snowbimmer6327.00
jmg19247.50
      01-15-2023, 12:26 PM   #12
snowbimmer
Colonel
snowbimmer's Avatar
United_States
6327
Rep
2,057
Posts

Drives: 2022 M850 GC - Carbon Black
Join Date: Feb 2017
Location: PDX

iTrader: (0)

Garage List
2022 M850 GC  [9.67]
Quote:
Originally Posted by BMWCCA1 View Post
Increasing overall tire height (diameter) with the same wheel diameter will only decrease the handling capability of your car with respect to turn-in due to slip-angle. If you're looking for increased comfort, you shouldn't have bought a sport model in the first place! Just get a 530i xDrive and leave those snow tires off your M5!
I have been on the elusive search for the "perfect" car for several years. I want fast, I want luxury, I want canyon carving handling and I want drivability in the city. The M550 was great, but the M5 beckoned. My base 2019 M5 proved to be too stiff in the city. My 2021 LCI Comp was spectacular, fixing many of the problems with the base - but, still too jarring (for a 130k car) in the city for me. The M850 is still stooopid fast, luxurious, rides better - at the expense of giving up some of the suspension goodies. It's also a bigger car and a heavier car. I don't know why they didn't give it the same tires and wheels as the M8. The OEM tires are really low profile. I don't know why you think I shouldn't have bought a sport model, when all I'm trying to do is get back to the size tires that were on my M5, and are also on the M8.

I've taken many 4,000 mile two week trips in the last few years. We go 300 miles/day and try to stay off the freeways. The car is a blast on the two laners, but obviously not M5 territory. It's most noticeable when I push it, but that's not really all that practical with someone else in the car telling you to slow down. (Sheesh. Women...) The wider wheel I am also going to would help negate any increase in tire height.

As far as snow tires, sometimes you just need some effing snow tires
Name:  Car3.jpg
Views: 1265
Size:  610.0 KB
Name:  Car11.jpg
Views: 1256
Size:  631.6 KB
By the way, these snow tires were an 8" square set from my M550 - and they sucked for a car this big. But, they got me there and back. I bought the car car 2 days before the trip and it's all I could do. Luckily they were still in my basement. But, they are also the recommended BMW snow set for the M850.

Same trip, the next day
Name:  Car58.jpg
Views: 1251
Size:  409.6 KB

This winter I am running Michelin Alpin4 tires on the OEM wheels.........much, much, much better.
Name:  Snowy Skyline.jpg
Views: 1261
Size:  396.1 KB


Quote:
Originally Posted by Llarry View Post
I think the OP is more concerned with appearance.
Its a twofer: more sidewall plus less wheel gap. I doubt is there is a single M8 owner that says, "Ya know, Ima gonna go down a profile. I just want more space between my fender and the tire."

Last edited by snowbimmer; 01-16-2023 at 07:43 PM..
Appreciate 1
DrFerry6803.50
      01-15-2023, 12:28 PM   #13
snowbimmer
Colonel
snowbimmer's Avatar
United_States
6327
Rep
2,057
Posts

Drives: 2022 M850 GC - Carbon Black
Join Date: Feb 2017
Location: PDX

iTrader: (0)

Garage List
2022 M850 GC  [9.67]
Quote:
Originally Posted by Onesie View Post
The problem with your car is the xdrive.
You can change the tire diameter but you need to keep all 4 in the same ratio as stock.
The M8 uses different diameters front/rear but it’s setup like that. That’s why you can’t go as wide in the same proportion as the M8.

Figure out the original proportions, up 1 size on both axles and you should be good to go. Mind the fact the car will drive a bit differently and not necessarily better. I’ve done this before (not in an 8) and I prefer the stock setup, but YMMV.
I think I see where you're coming from. I've investigated this a lot. The M5 and M8 run with rears slightly bigger in diameter
Front Dia: 27.58" Rear Dia: 27.86"

The BMW M5 & M8 snow set uses a 19" wheel and goes down a width to 265 in front, making the gap wider
Front Dia: 27.34" Rear Dia: 27.98"

The 19" OEM summer set up (which I also ran) was
Front Dia: 27.66" Rear Dia: 27.98"

In all cases the rears are between 1% to 2% larger in diameter. So, my question, since you bring up x-drive, does BMW engineer the car
for this larger wheel diameter in the rear - OR, do they just find the tires that fit within certain tolerances and call it a day?


The M850, on the other hand is just the opposite: The fronts are a larger diameter than the rears
Front Dia: 26.76" Rear Dia: 26.50"

My new setup with 10mm wider tires, and keeping as close to OEM sizing as possible take me to:
Front Dia: 27.03" Rear Dia: 26.73"

I could then go up one profile, but then I'm pushing 28" diameters, but I could still keep the fronts slightly taller than the rears.

And, again, did BMW engineer the M850 with the expectation that the front tires are to be taller than the rears? The Alpina B8, which is a souped up M850,
actually uses the taller tires. like the M5 and M8.

I think I'll probably just stay within OEM sizing and call it good.

Last edited by snowbimmer; 01-16-2023 at 07:41 PM..
Appreciate 1
DrFerry6803.50
      01-15-2023, 12:52 PM   #14
BeEmVe
Lieutenant
United_States
279
Rep
586
Posts

Drives: '14 X1 x28i M-Sport
Join Date: Sep 2013
Location: on the road to perdition

iTrader: (1)

If you have not used the tire calculator before here is a link: https://tiresize.com/comparison/
Appreciate 0
      01-15-2023, 01:14 PM   #15
snowbimmer
Colonel
snowbimmer's Avatar
United_States
6327
Rep
2,057
Posts

Drives: 2022 M850 GC - Carbon Black
Join Date: Feb 2017
Location: PDX

iTrader: (0)

Garage List
2022 M850 GC  [9.67]
Quote:
Originally Posted by BeEmVe View Post
If you have not used the tire calculator before here is a link: https://tiresize.com/comparison/
Thanks. I have several I use.

This is also good for quick and dirty
https://www.discounttire.com/learn/tire-size-calculator

This is good for offsets and poke calcs
https://willtheyfit.com/
Appreciate 0
      01-15-2023, 02:44 PM   #16
HighlandPete
Lieutenant General
6548
Rep
15,857
Posts

Drives: BMW F11 535i Touring
Join Date: Mar 2007
Location: Scotland, Highland Region

iTrader: (0)

Quote:
Originally Posted by snowbimmer View Post
The M850, on the other hand is just the opposite: The fronts are a larger diameter than the rears
Front Dia: 26.76" Rear Dia: 26.50"

....

And, again, did BMW engineer the M850 with the expectation that the front tires are to be taller than the rears?
Something to keep in mind. Are you calculating the diameter from generic sized tire charts/calculators? That is not 'definitive' sizing for 'star' marked approved tires.

Also remember those are nominal sizes, not allowing for manufacturing tolerances, (even within the appropriate standards), can be quite wide. BMW could well be setting tolerances which may make front and rear RC (rolling circumference) for the OE tires different than it appears.
Appreciate 1
snowbimmer6327.00
      01-15-2023, 02:51 PM   #17
shawnhayes
Major
1950
Rep
1,399
Posts

Drives: 23X5E,24M3 CS,24 i4, 25 M4 CS
Join Date: Aug 2015
Location: Virginia

iTrader: (0)

We had to learn this the hard way in the GT-R world. Many manufacturers and tire size calculators that were "just right" still blew center differentials over and over.

A guy named Shep from ShepTrans (famous in the EVO/DSM/GT-R world for drivetrain) finally gave us the reality. Only way to know for sure is to install the damn tires, and put them on the car at running pressure, and mark them and do a slow rollout.

Unless they were REAL close, you'd eventually blow the center diff.

BMW's system is probably a little more tolerant. Who knows? I don't be the one to find out. I install either BMW "listed" tires and setups, or I install "square" (same tire all the way round) setups.

OP, reality is you can change the OD, but lots of unpredictables can occur as the result. Just giving you a suggested pathway to ensure safety.

Shawn
Appreciate 2
snowbimmer6327.00
Llarry21181.00
      01-15-2023, 04:02 PM   #18
snowbimmer
Colonel
snowbimmer's Avatar
United_States
6327
Rep
2,057
Posts

Drives: 2022 M850 GC - Carbon Black
Join Date: Feb 2017
Location: PDX

iTrader: (0)

Garage List
2022 M850 GC  [9.67]
Quote:
Originally Posted by HighlandPete View Post
Something to keep in mind. Are you calculating the diameter from generic sized tire charts/calculators? That is not 'definitive' sizing for 'star' marked approved tires.

Also remember those are nominal sizes, not allowing for manufacturing tolerances, (even within the appropriate standards), can be quite wide. BMW could well be setting tolerances which may make front and rear RC (rolling circumference) for the OE tires different than it appears.
Quote:
Originally Posted by shawnhayes View Post
We had to learn this the hard way in the GT-R world. Many manufacturers and tire size calculators that were "just right" still blew center differentials over and over.

A guy named Shep from ShepTrans (famous in the EVO/DSM/GT-R world for drivetrain) finally gave us the reality. Only way to know for sure is to install the damn tires, and put them on the car at running pressure, and mark them and do a slow rollout.

Unless they were REAL close, you'd eventually blow the center diff.

BMW's system is probably a little more tolerant. Who knows? I don't be the one to find out. I install either BMW "listed" tires and setups, or I install "square" (same tire all the way round) setups.

OP, reality is you can change the OD, but lots of unpredictables can occur as the result. Just giving you a suggested pathway to ensure safety.

Shawn
Great points, guys. It seems there would be some favorable tolerances built into the BMW 4WD systems, because there are thousands of folks here on the forums changing their rides from OEM tires and wheels to aftermarket products. (Granted, 2WD much less critical, so G8x M3s and M4s are newer to the game). I only seem to read about people with rubbing problems and strut clearances, which they fix, but never any differential problems (unless they just keep quiet)

I can only base my most experience off my 2 M5s. The OEM 20" summer wheels have a front to back diameter difference of 0.28", or 1.02%.

The OEM 19" summer set has a front to back diameter difference of 0.32", or 1.16%.

The BMW approved 19" snow set has a front to back diameter difference of 0.64", or 2.34%.

(The above based on nominal sizing, because I have no other data to go on)

"They" say to always have your front to back diameters within 1% on an AWD car. The OEM summer 20s and 19s are close to 1% (still over), but the winters are are considerably over a 2% difference in diameter. I saw no ill effects during 3 winter seasons, so I'm thinking we may have a little leeway here.

And shawnhayes, what did you mean by "REAL" close when you do the roll out? How close is REAL close in Shep's world to not blow out the center diff?

Thanks for the input. This is what I've been looking for.
Appreciate 1
DrFerry6803.50
      01-15-2023, 04:13 PM   #19
Accentu8
Second Lieutenant
Accentu8's Avatar
722
Rep
249
Posts

Drives: MY24 Porsche Taycan
Join Date: Nov 2022
Location: Texas

iTrader: (0)

Garage List
I have been driving on B roads and freeways as well as taking some quick corners for 5 days now and I’ve noticed no detriment to handling and ride is much better and much quieter with 40 front and 35 rear sidewalls. I don’t have xdrive. I love the new Continental ExtremeContact DWS06+. It’s an ultra high performance A/S that Tire Rack rated very high and it has great customer reviews as well. I’m very happy with my choice and filled up the wheel well nicely as well as increasing ride height by 1/2” which in these low slung cars certainly not a bad thing.
Attached Images
 
__________________
MY24 Porsche Taycan | Neptune blue | Black |

MY24 Audi SQ5 Prestige | Mythos black metallic | Magma red Nappa

Retired: MY23 BMW 840i Coupe | MY21 Audi SQ5 | MY19 Audi A6
Appreciate 1
snowbimmer6327.00
      01-15-2023, 04:16 PM   #20
snowbimmer
Colonel
snowbimmer's Avatar
United_States
6327
Rep
2,057
Posts

Drives: 2022 M850 GC - Carbon Black
Join Date: Feb 2017
Location: PDX

iTrader: (0)

Garage List
2022 M850 GC  [9.67]
Quote:
Originally Posted by 23TripleBlack View Post
I have been driving on B roads and freeways as well as taking some quick corners for 5 days now and I’ve noticed no detriment to handling and ride is much better and much quieter with 40 front and 35 rear sidewalls. I don’t have xdrive. I love the new Continental ExtremeContact DWS06+. It’s an ultra high performance A/S that Tire Rack rated very high and it has great customer reviews as well. I’m very happy with my choice and filled up the wheel well nicely as well as increasing ride height by 1/2” which in these low slung cars certainly not a bad thing.
Ah, no xDrive. I doubt you'll have problems, then.

Damn, that sure looks good. I had a Donington M5 - my favorite color. Skyscraper is close.
Appreciate 1
Accentu8722.00
      01-15-2023, 05:06 PM   #21
shawnhayes
Major
1950
Rep
1,399
Posts

Drives: 23X5E,24M3 CS,24 i4, 25 M4 CS
Join Date: Aug 2015
Location: Virginia

iTrader: (0)

Quote:
Originally Posted by snowbimmer View Post
And shawnhayes, what did you mean by "REAL" close when you do the roll out? How close is REAL close in Shep's world to not blow out the center diff?

Thanks for the input. This is what I've been looking for.
For the GT-R (way different system than the x-drive, but I don't understand all the nuances yet, but the suggestion is that the weak point is the center transfer case - not a heavy duty piece frankly), the 1% was certainly within what Shep was talking about. But, that's PRESUMING what you're TOLD is actually TRUE. Manufacturers LISTED measurements are frequently "meh" from what we found.

If you put them on the car, and mark where the tires are, and do 3-10 revolutions, if they are within 1% of the rotation (3.6 degrees) I feel pretty confident they'd be perfectly safe. You'd be shocked how much different 3.6 degrees x 10 rotations looks like. (Imagine 36 degrees of difference between the marks on the tires).

So, 1%, probably okay.

Shawn
Appreciate 1
snowbimmer6327.00
      01-15-2023, 05:17 PM   #22
HighlandPete
Lieutenant General
6548
Rep
15,857
Posts

Drives: BMW F11 535i Touring
Join Date: Mar 2007
Location: Scotland, Highland Region

iTrader: (0)

Quote:
Originally Posted by snowbimmer View Post
Great points, guys. It seems there would be some favorable tolerances built into the BMW 4WD systems, because there are thousands of folks here on the forums changing their rides from OEM tires and wheels to aftermarket products. (Granted, 2WD much less critical, so G8x M3s and M4s are newer to the game). I only seem to read about people with rubbing problems and strut clearances, which they fix, but never any differential problems (unless they just keep quiet).
Latest xDrive systems have been greatly revised, compared to the original designs, back in the days of models like the E83 X3. On those models tire tolerances were very critical and many transfer cases were compromised/destroyed with generic tire fitments. (Personal experience, my local tire shop would only fit star marked tires to the E83 X3, due to too many drivetrain issues with non approved fitments).

Transfer cases in the current M models have much more 'RWD only' engagement. The BMW M VTG control only applies torque to the front axle/wheels in limited situations. This means the multidisc clutch is running open much more of the time. This at least partly explains how BMW can be more flexible with M model tire selection.

Even in the more regular models, there are technical features to improve heat management and reduce wear. Plus changes to oil levels and flows, which reduce churning losses, aids efficiency.
Appreciate 1
snowbimmer6327.00
Post Reply

Bookmarks


Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -5. The time now is 06:13 PM.




5post
Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
1Addicts.com, BIMMERPOST.com, E90Post.com, F30Post.com, M3Post.com, ZPost.com, 5Post.com, 6Post.com, 7Post.com, XBimmers.com logo and trademark are properties of BIMMERPOST